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Hotspot issues for COMSOL Multiphysics simulated lithium battery

2019-02-26 来源:亚科官网

With the continuous exploration of science by humans, the research on lithium-ion batteries is no longer dependent on experiments, but modeled by software, and the electrochemical simulation is used to predict the performance of the battery in various aspects, and then a detailed experimental plan is formulated for experimental verification.

With the development of simulation technology, simulation technology has been applied to the research and development of more and more scientific research fields. As a complementary tool to the experiment, COMSOL Multiphysics can:

(1) Simulate each experimental scheme by battery modeling before the experiment, estimate the experimental results, narrow the parameter range, and improve work efficiency.

(2) Simulating the internal electrochemical process during battery operation helps researchers study the internal process of the battery. Manage battery operation more efficiently by simplifying, simulating, and analyzing battery models.

(3) Combined with experimental data, the content of the article is persuasive, predictive, novel, and can be published to advanced journals in the field.

At present, the five research hotspots of thermal management, polarization, SEI film stability and electrode/electrolyte interface problems of lithium-ion batteries can be simulated by COMSOL Multiphysics.

1. Application of COMSOL Multiphysics in battery thermal management

With the continuous upgrading of power equipment, the battery has gradually developed toward large size and modularization. The problem of battery heat generation has become increasingly prominent, and battery thermal management has become one of the research priorities in the battery field. During the charging and discharging process, heat is generated inside the battery. If it is not dissipated in time, the temperature will rise and exceed the normal working range of the lithium battery: (safe temperature range), which will affect the working condition, cycle efficiency, capacity and power of the battery, which in turn affects the reliability, safety and longevity of the equipment. Establishing a lithium battery thermal model is the basic method for studying the temperature distribution and variation of lithium ion batteries. By studying the thermal effects of the battery, the battery structure is optimized and the safety characteristics of the battery are improved.

COMSOL Multiphysics provides ample physics interface that allows users to study the thermal effects of lithium-ion batteries by coupling lithium-ion battery interfaces to heat transfer interfaces. The software has a simple and clear boundary condition setting interface, which is easy for users to get started. At the same time, it also has a clear visual interface, which can visually observe the temperature distribution inside the lithium ion battery.

In addition to visually observing the temperature profile, COMSOL Multiphysics also provides a parametric sweep function that helps us understand the effects of different parameter values on battery temperature and the effect of temperature on other battery performance.

2. Application of COMSOL Multiphysics in battery capacity attenuation

In lithium ion batteries, in addition to the redox reaction occurring during lithium ion deintercalation, there are a large number of side reactions such as decomposition of electrolyte, dissolution of active materials, deposition of metallic lithium, etc. Side reactions and degradation processes can lead to a variety of undesirable effects that are irreversible and can result in loss of battery capacity. Generally, batteries are aged due to multiple complex phenomena and reactions occurring at different locations. In the load cycle, the stage of the battery is different, and the degree of degradation is different depending on the potential, local concentration, temperature, and current direction. The material of the battery is different, and the degree of aging is also different. The combination of different materials (such as the "cross effect" of the electrode material) may further accelerate the aging. COMSOL Multiphysics can help researchers establish a battery aging model to quantitatively analyze various factors that cause battery aging. It can clearly understand the cause of battery aging, establish research goals, focus on major problems, improve scientific research efficiency, and accelerate the development process of ion batteries.

Numerous studies have shown that battery side reactions make the SEI film gradually thicken, which is the main reason for the decrease of battery capacity. Therefore, we can also use COMSOL Multiphysic to study the relationship of SEI film with time, study the formation mechanism of SEI film, and enhance the stability of SEI film, reduce the negative electrode/electrolyte interface impedance.

3. Application of COMSOL Multiphysics in analyzing battery short circuit

The battery forms lithium dendrites during charging, piercing the battery separator, causing a short circuit inside the battery, or being externally mechanically pierced, causing the battery to be short-circuited. Long internal short circuits can cause self-discharge of the battery and local temperature rise. If the temperature exceeds a certain value, the electrolyte may start to decompose due to the thermal reaction, resulting in thermal runaway, reducing the cycle performance of the battery and making the battery have safety hazards. Modeling and analysis of thermal runaway problems caused by short-circuiting of batteries with COMSOL Multiphysics

4. Application of COMSOL Multiphysics in analyzing electrochemical impedance spectroscopy of batteries

Electrochemical impedance spectroscopy (EIS) is one of the most powerful tools for studying the electrochemical processes occurring at the electrode/electrolyte interface. It is widely used to study the intercalation and extraction process of lithium ion in the electrode active material of lithium ion battery. Applying a frequency-variable potential disturbance to the battery electrode provides an in-depth understanding of the various properties and processes of the battery through impedance response: at high frequencies, short-term processes such as capacitance, electrochemical reactions, and local resistance can affect impedance. On the other hand, at low frequencies, the diffusion of electrolyte and active material also affects the impedance. The EIS characteristics of chimeric electrodes can be analyzed by COMSOL Multiphysics, and the attribution of time constants in EIS spectra can be discussed. The related kinetic parameters of lithium ions in the process of insertion and extraction of positive and negative active materials, such as charge transfer resistance and activity, are discussed. The electronic resistance of the material, the diffusion, and the dependence of the lithium ion diffusion on the polarization potential and temperature of the electrode through the resistance of the SEI film.

5. Application of COMSOL Multiphysics in analyzing the ratio of battery electrode materials

In order to improve the stability of the battery electrode material, generally, the positive and negative electrodes comprise a plurality of intercalation materials, especially a positive electrode material, usually a mixture of a plurality of materials, such as a transition metal oxide, a multilayer oxide, and an olivine. These materials can have different design properties (such as volume fraction and particle size), thermodynamic properties (such as equilibrium point and maximum lithium ion concentration), transfer properties (such as solid diffusion coefficient), and kinetic properties (such as intercalation reaction rate constants). Different material ratios will have a great impact on the overall performance of the battery. If the experiment is used to continuously find the optimal ratio, the workload is large and the efficiency is not high. By using COMSOL Multiphysics to analyze the ratio of different materials through battery modeling, the workload can be reduced, thereby reducing the research range of experimental parameters and saving manpower and material resources.

Edited by Suzhou Yacoo Science Co., Ltd.